Loudspeakers with a moving cone and coil are very old and have evolved little since their invention. To this date, the scheme is maintained of a cone of cardboard or paper that is driven by a coil in an intense magnetic field, which when excited by an alternating current makes the cone vibrate to thereby reproduce the sound.
As far as the authors of the present invention are aware, there is available in the market a flat loudspeaker of the American company Sound Advance that represents an evolution of the aforementioned loudspeakers. Sound Advance substituted the traditional cardboard or paper cone by a special panel with one flat face made of expanded polystyrene and which, by the special design of its rear face, allows the panel to reproduce the range of audio frequencies in an approximately linear fashion.
In this way, the flat speaker of Sound Advance is none other than a common magnetic system impelling a special panel whose acoustic characteristics are achieved by its particular design and construction. The achievement of Sound Advance was the design, formulation of the material and the construction of the special panel that confers its acoustic properties and simultaneously its flatness.
The present applicant has a patent application in Chile with application number 2598-99 in which is described an electromechanical and electromagnetic device that allows to transform an open roof panel or sandwich type panel of plaster and cardboard, commercialised under the name Pladur® into a high-fidelity electro-acoustic transducer.
In the device object of this patent the subtlest parameters have been handled, such as the shape and dimensions of the contact surfaces with the panel, as well as the nature of the adhesives used to attach it to said panel, the dimensions, shape and type of the materials of the component parts, particularly of the coupler, in order to provide an infinitely equalizable electro-acoustic device that allows obtaining a linear response (40–18,000 Hz±3 dB) from a common market-available continuous ceiling, partition or wall panel, made of materials such as mineral fibre, plasterboard, multi-laminated wood, etc. when suitably installed therein, thereby converting it into a high-fidelity flat radiator with wide dispersion and invisible in its place of installation.